The invention relates to a spray gun in particular for the spraying of abrasive media, or rather media to which abrasive materials have been added, comprising a valve that is operable by means of a nozzle needle, which valve is arranged in the gun head near the outlet opening for the media, and comprising an operating and return device for the nozzle needle.
Spray guns of the abovementioned type are known, whereby these as a rule are used to process 2-component lacquers or other materials, to which as a rule abrasive particles are additionally added, for example, to apply an under-bottom carriage protection onto vehicles, or to process 2-component polyurethane lacquers. It is known that the processing time, potlife, of these lacquers is relatively short so that they can be mixed only shortly prior to the spraying. A problem when using the spray guns for such lacquers is that the spray guns must be cleaned with solvents after the work has been done, in order to prevent a hardening of the already mixed lacquers still in the gun which is time-consuming and expensive. Solvent channels for this purpose are, as a rule, provided in the spray gun, through which channels, by supplying solvents, the material of the two components already mixed in the spray gun is washed out. When fully carried out, this process also requires, as a rule, a disassembly of the nozzle system being used.
In order to keep the mixing channel for the two or more components relatively short, it is known to supply the individual components just shortly in front of the nozzle outlet. Achieving a satisfactory mixing of the components in the remaining short channel is a problem. The valve is as a rule operated by pressure-air-operated nozzle needles, which makes the spray gun not only awkward to handle but moreover also expensive.
The basic purpose of the invention is to provide a spray gun of the abovementioned type in such a manner that it is self-cleaning, can process several components with abrasive material, is inexpensive to manufacture, and is light and thus easy to operate.
This purpose is attained according to the invention by the nozzle having a channel that ends in the outlet opening of the spray gun, in which channel the nozzle needle is moveably supported. The channel has at least one bore that laterally enters the channel and is utilized for supplying the media. The bore can be closed off by the nozzle needle, which has a diameter chosen to match the diameter of the channel. The length of the nozzle needle is chosen such that when the nozzle needle is in a resting position, it terminates at least at the outlet opening of the spray gun.
This nozzle needle, which is spring-loaded, is thus moved in the resting position at least into the plane of the outlet opening so that all of the material already mixed in the channel of the nozzle is moved out of the nozzle. Since the diameters of the nozzle needle and the channel are the same, not only are the bores for the supply of the media tightly closed off when the nozzle needle is moved to the resting position, but moreover, all mixed material is removed from the channel. No solvents whatsoever are needed for cleaning the spray gun. The spray gun is self-cleaning since, upon the conclusion of each spraying process, the spray gun automatically cleans itself by means of the nozzle needle.
The nozzle is manufactured of a hard metal so that it is insensitive to abrasive material, thus the self-cleaning and well sealing action of the nozzle is completely maintained even after extended use. A nozzle of a ceramic material is also particularly advantageous.
In order to achieve an exact mixing of the two media, the bores through which the media are separately supplied, lie advantageously in one plane and are oriented perpendicular to the channel, whereby the diameters of the bores are smaller than the diameter of the channel. Furthermore, the bores are elevationally offset from one another so that when media is sprayed into the channel a turbulent zone is constructed, which results in a complete mixing of the media in the short path.
The nozzle needle is loaded by a spring, which moves the needle into the closed position when the operating lever is released.
The nozzle is advantageously arranged in an insert piece, in which bores for lines which supply the media are arranged. These lines are connected directly to the nozzle, whereby these lines are advantageously pivotal relative to the nozzle and thus to the insert This further improves the handling ability of the spray nozzle.
To allow for production of a broad spray, the outlet opening of the nozzle is followed by a slot-shaped enlarging opening. In addition, the outlet opening of the nozzle is oval shaped, and the larger axis of the oval opening is advantageously arranged perpendicularly with respect to the slot-shaped opening. This results in an even spray projection extending over a large distance.
The nozzle needle is advantageously connected to an operating rod which is loaded by the pressure spring The operating lever of the spray gun has an abutment, which cooperates with a shoulder of the operating rod so that the spray gun can be easily manually operated, and does not require any expensive additional energies, like pressure air, etc. for its use.